The invention concerns an installation for hardening tubular concrete workpieces in chambers which are open at the top, can be closed with cover plates, can be filled with vapour and which can be charged with the aid of an overhead travelling crane bearing the load of the workpieces.
After tubular, concrete workpieces such as concrete pipes, tubbing rings or well casings have been removed from the mould, these workpieces must be placed into an interim storage facility to allow the concrete to harden. This is done with consideration being given to the fact that the concrete is yet to harden and can only be subjected to minimal load in an upright position. Overhead travelling cranes with a hoisting device (AT 405 395 B) are used to transport the tubular workpieces which include an encompassing, metallic bottom ring for setting them down. Said cranes consist of a supporting frame which runs above the workpieces to be picked up and brackets which encircle the exterior of the workpiece. Said brackets reach under a flange located in the metallic bottom ring by means of adjustable dogs which are perpendicular to the axis of the workpiece and which lift it. With the aid of such overhead travelling cranes, the workpieces can be stored in an appropriate storage area and allowed to harden after they have been removed from the mould and can then be transported from this storage area after hardening.
If the tubular workpieces are subjected to vaporisation to facilitate more effective hardening, the workpieces must be placed in chambers for hardening which are closed for vaporisation. To achieve this, chambers are known which are open at the top and which are closed by means of cover plates. To load and unload the chambers the cover plates must be opened before the workpieces can be inserted or removed. Due to the size of the relatively heavy cover plates, their opening and closing requires measures involving significant effort which must not hinder the movement of the workpieces either. In order to avoid having to allocate a special opening and closing device for each cover plate, in known installations the cover plates share a common lifting device which is driven along the row of chambers, with attention needing to be paid to the transportation routes of the overhead travelling crane employed for workpiece charging in order to avoid mutual interference. In order for charging and discharging to occur, the individual workpieces do not only have to be lowered into and lifted out of the single chambers which are open at the top, but must also be transported away from the chambers at a distance above them.
The aim of the invention is to provide an installation for hardening tubular concrete workpieces of the type described at the outset such that the construction for opening and closing the cover plates can be significantly simplified.
The invention fulfils this aim by incorporating a holding device for the cover plates into the overhead travelling crane used for the workpieces.
As the overhead travelling crane used for the workpieces includes a holding device for cover plates, there is no longer any need for a separate lifting device for the cover plates, which are now lifted off the chambers and replaced onto them by the overhead crane used for the workpieces before and after the workpieces have been transported. One must only ensure that the weight of a cover plate does not exceed the permissible load rating of the overhead crane. In order to suffice with an overhead crane designed to work with the weight of the workpieces, the chamber cover plates can be divided into removable cover plate segments of less weight accordingly.
In order to set down the cover plates removed from the chambers, a stackable storage facility for the cover plates can be located at the end of the row of chambers which are oriented in the direction of travel of the overhead crane so that the workpieces can be transported without interference after the cover plates have been stacked. A particularly simple construction constellation results in this case if the stackable storage facility for the cover plates is arranged in the area near the discharging station of a feeder conveyor for the workpieces to be hardened and/or in the area near the charging station of a discharge conveyor for the hardened workpieces as in this case a workpiece requiring hardening can be picked up and transported into the opened chamber after the cover plate has been set down without the overhead crane having to make an additional empty run. Similarly, no further conveyer travel is required for the overhead crane to convey a stockpiled cover plate to the open chamber after a hardened workpiece has been removed from it.
Although the overhead crane for the workpieces can be provided with a holding device designed specifically for each cover plate""s dimensions, a particularly simple construction constellation results if the hoist for the workpieces is insertable. Preferably, this hoist shall consist of a supporting frame which runs above the standing workpieces to be picked up and of brackets which are arranged on the supporting frame and which encompass the workpieces externally and which have dogs which are adjustable along an axis lying at right angles to the axis of the workpiece and grip under a flange located on the bottom ring of the workpieces. In this case the chamber cover plates only need to have pick-up recesses which have been modified to accommodate the bracket arrangement for the dogs, which are located on the brackets of the hoisting device, to then be able to be inserted into the pick-up recesses when adjusted accordingly, connecting each cover plate to the bracket of the hoist.
An especially advantageous way of handling the cover plates to be opened and closed during charging of the chambers can be achieved if the opened chambers are not closed with a cover plate from the stackable storage facility, but with the cover plate from the chamber opened immediately beforehand which is then to be loaded. This means that after a chamber cover plate has been stacked in the storage facility, the chamber concerned shall not be closed with the stacked cover plate any longer, but preferably with the cover plate of the neighbouring chamber which has been opened to remove the fully hardened workpieces and to receive workpieces requiring hardening, while the cover plate stacked in the storage facility is to be used to close the final chamber opened.